Boosting hydrogen evolution of nickel phosphide by expanding built-in electric field with tungsten oxide

Manipulating the built-in electric field (BIEF) in the catalyst to regulate the electronic structure and improve the carrier transport is a promising approach, but it is rarely applied in the design of hydrogen evolution reaction (HER) catalysts. In this study, the electrochemical microenvironment of nickel phosphide supported on nickel foam (Ni2P/NF) has been modified by introducing tungsten oxide (WO3) through simple ion group exchange strategy, thereby expanding the BIEF and enhancing the electron transport property. As a direct outcome, the target catalyst (20-WO3/Ni2P/NF) exhibits ultralow overpotential of 301 mV at high current density of -1000 mA cm-2. Additional characterization and density functional theory calculations demonstrate that the WO3 can not only serve as a new hydrogen adsorption active site, but also effectively decrease the dissociation energy of water molecules at the nickel site, which results in rapid production and consumption of protons and enhancing the overall catalytic activity.